Möbius dissolution process for recycling of plastics

Less CO2 emissions, less use of materials and less plastic litter. Over the past decades, plastic waste treatment policies have promoted incineration combined with energy recovery in order to reduce the amount of waste going to landfill. This approach was successful in the Netherlands, but the policy change towards becoming circular by 2050 means that new technologies are needed to recycle plastics. TNO has developed a selective dissolution process to recycle polymers and additives from plastic waste in a resource-efficient and environmentally-friendly way.

Closing the plastic cycle

There are various recycling technologies to close the plastic cycle. Nowadays, about 15% of our plastics are recycled. These are mono-streams of waste plastics from packaging (e.g. bottles, trays, pouches, bags), waste electronics (e.g. refrigerator interiors) and construction waste (e.g. window frames).

These streams are mechanically recycled into plastic granulate that can be reused to make small objects and non-food packaging, whereas mixed plastics are converted into massive objects such as garden furniture. To increase the amount of recycling, TNO is investing in new physical and thermochemical recycling technologies to handle more complex waste streams in combination with the production of feedstock for high-end applications.

Recycling of plastics into purified polymers

TNO has set up a physical recycling technique under superheated conditions for the selective dissolution of plastics. This is combined with the removal of impurities from the polymer solution before recovering the cleaned polymer. This technology is based on the use of a low-boiling solvent at an elevated temperature in order to facilitate the dissolution of the polymers. The hot polymer solution has a sufficiently low viscosity to allow for the use of conventional separation techniques, such as filtration and adsorption, that remove additives and impurities that were present in the plastics.

These components include small particles (such as pigments) and molecular compounds (such as plasticisers and flame retardants that were originally added to improve the properties of the plastics). After the removal of the additives, purification and recovery of the polymers is carried out. This TNO technology is thus suitable for the recovery of cleaned polymers from multi-material plastics and the valorisation of the recovered additives.

Möbius dissolution process

This technology and the equipment are named after the symbol of circularity: the Möbius strip. A potential advantage of this technology compared to current state-of-the-art dissolution processes is that it is a potentially energy-efficient operation. This is because the solvent can be evaporated at a low temperature.

Furthermore, the use of a low-boiling solvent allows for the recovery of polymers with a low residual solvent content. Over the past years, this technology has been developed by a small team of scientists, engineers and technicians who started with polymer dissolution in a semi-batch set-up. This set-up was scaled up from a working volume of tens of millilitres to two litres, enabling the initial production of samples of a few grams. This has risen to a scale of hundreds of grams in the present Möbius 1.0 set-up. Functionality was also added to the equipment in the form of separation and recovery steps for both additives and cleaned polymers.

The whole value chain for plastics

So far, joint projects in which the Möbius technology has been developed and applied include national and European projects with research institutes and industrial partners. The projects span the whole value chain for plastics, including waste electronics and waste multilayer packaging films (Plast2bCleaned, Impres, Pack-CE, Mucipack).

At the same time, synergy has been sought out with TNO groups working on thermochemical recycling (Petten) and mechanical recycling and the redesign of plastic products (Eindhoven/Geleen), as well as with the groups in Utrecht that are working on Impact Assessments and sensors/detection.

What’s next?

The next stage will be to further develop the technology and build an even more scaled-up and semi-continuous set-up in which the solvent can be recycled (Möbius 2.0). This set-up will be used to produce samples for our partners at a kg scale so that they can validate the properties of the recycled polymer for their products.

Another objective is to extend the application area of the technology to the recovery of clean polymers from other plastic waste streams, such as from domestic applications (e.g. carpets), end-of-life-vehicles and end-of-life construction materials.

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